Founding a Religion in a city that already has one

In Civilization VI can I found a religion in a city that already has one? Will the city have the just-founded Religion, despite it having only one follower, or will it stick to the religion of most of its citizens, effectively pre-emptying the spread of the new Religion?

Civilopedia seems to say conflicting things about this:

Founding your Religion: "Once your Religion is founded, all of your cities with Holy Sites will automatically convert to the Religion"

Religious Units and Pressure "If more than half the citizens in the city are Followers of a particular Religion and that Religion has the majority of Followers in that city, that Religion will become predominant in that city"

So, which of these effects predominate?

Solution 1:

Yes you can.

To found a religion, you need a prophet. You can only ever gain one prophet. Hence, the religion present in the city you want to found your religion in, and thus make it your holy city, is the religion of another player.

Once you found your religion, all your cities with holy cites convert to your religion as states in the Civilopedia. There is no conflict with the entries you stated. The conflict arises from your assumption that the cities would gain your religion by having one citizen of your religion. This is not true. Founding a religion will flip as many citizens as needed to make your religion the majority religion in those cities.